JPH0544036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an image forming apparatus that forms an image by developing an electrostatic image with a developer such as toner. Conventional image forming apparatuses of this type require a mechanism to transfer the developed image by heating and a mechanism to fix the transferred developed image, which complicates the process and reduces power consumption. It has the disadvantage of being large. Furthermore, conventionally, a photoreceptor with a short life span must be used as an image forming member. Therefore, it is an object of the present invention to reduce the process
Another object of the present invention is to provide an image forming apparatus that can reduce power consumption for transfer and fixing and has a long life. Examples will be described below with reference to the accompanying drawings. FIG. 1 shows an example of application to double transfer electrophotography. In the apparatus shown in FIG. 1, a dielectric cylinder 73 is used to support the electrostatic latent image during the period between latent image formation and toning, or in the case of electrophotographic apparatus, between image transfer and toning. The dielectric layer 75 has a sufficiently high resistivity. For example, the resistivity of this dielectric layer 75 is 10 ¹² ohmcm. Further, the preferred thickness of the dielectric layer 75 is 0.0025 to 0.0075 cm. Additionally, the surface of the dielectric layer 75 is coated to provide complete toner transfer to the light-receiving member sheet 81.
It is highly abrasion resistant and relatively smooth, preferably with a finish better than 25 micro-cm rms. Dielectric layer 75 also has a high modulus so that it is not significantly distorted by the high pressures in the transfer nip. Many organic and inorganic dielectric materials can be used in dielectric layer 75.
It is suitable for For example, glass enamel can be deposited and fused onto the surface of a steel or aluminum cylinder. Flame- or plasma-sprayed dense aluminum oxide can also be used instead of glass enamel. Plastic materials such as polyamides, polyimides and other durable thermoplastics and thermosets are also suitable.
However, the preferred dielectric coating is
It is anodized aluminum oxide. A toning station 79 is provided to convert the electrostatic latent image formed on the dielectric layer 75 into a visible image. Although this station can use any conventional electrostatic toner, the preferred toner is the magnetic toner described in J.C. Wilson, U.S. Pat. No. 2,846,333, issued August 5, 1958. It is a single component that gives the tape electrical conductivity. The toned image is transferred and fused onto the receiving member sheet by high pressure applied between rollers 73 and 83. The lower roller 83 is composed of a metallic core 87 having an outer cover 85 made of engineering plastic on its outer circumferential surface.
The pressure required to achieve good fusing to plain paper is governed by factors such as the diameter of the roller, the toner used and the presence of a coating on the surface of the paper. Typical pressure is 100-700lbs/contact
The range is 2.5 linear cm. The function of the outer cover 85 is to absorb the high stresses introduced into the nip in the event of a paper jam or wrinkle. By absorbing the stress in the outer cover 85, the dielectric coated roller 73 will not be damaged during accidental paper wrinkles or jams.
Outer cover 85 is typically a nylon or polyester sleeve with a wall thickness in the range of 0.3 to 1.25 cm. For example, if a highly controlled web is to be printed for which paper wrinkles and jams are unlikely, there is no need to use this coating. A scraper blade 8 is used to remove residual paper dust, toner accidentally deposited on the rollers, and airborne dust and debris from the dielectric pressure cylinder and backup pressure roller.
9 and 91 are installed. Because substantially all of the toned image is transferred to photoreceptor sheet 81, a scraper blade is not necessary, but is desirable to promote reliable operation over long periods of time. A latent image discharge station 93 is provided to neutralize any small amount of residual electrostatic latent image remaining on dielectric layer 75 after transfer of the toned image. The act of toning and transferring the toned latent image to a plain paper sheet reduces the intensity of the electrostatic image, typically from a few hundred volts to a few tens of volts. In some cases, if the toning threshold is too low, the presence of a residual latent image creates a ghost image on the copy sheet, which is erased by discharge station 93. Such erasure can be accomplished by the apparatus of FIG. In FIG. 2, a roller 73 having a dielectric layer 75 is brought into contact with an open mesh screen 95 maintained at substantially the same potential as the conductive cylinder 77;
Or maintain some distance. The screen is mounted on the holder 99 and the AC corona wire 97 is placed behind the screen at a distance of typically 0.6 to 1.25 cm. For example, a high voltage alternating potential of 60 hertz is applied to the wire 97. Screen 95 provides a reference ground plane near the dielectric surface.
ground plane) and the AC corona wire 97 supplies both positive and negative ions. The local field at screen 95 due to the electrostatic latent image on dielectric layer 75 attracts the ions generated on the dielectric layer by corona wire 97, thus neutralizing most of the residual image. At very high surface velocities of dielectric layer 75, the residual charge can again become a ghost image. In this case, multiple discharge stations further reduce the residual charge to a level below the toning threshold. Also, erasure of the electrostatic latent image can be achieved by using a high frequency AC discharge between electrodes separated by a dielectric. Residual electrostatic latent images can also be erased by contact discharge. The surface of the dielectric must maintain intimate contact with a grounded conductor or a grounded semiconductor in order to effectively remove residual charge from the surface of dielectric layer 75, for example by a heavily loaded metal scraper blade. Charge can also be removed by a semiconductor roller pressed into intimate contact with the dielectric surface. FIG. 3 shows a partial cross-sectional view of semiconductor roller 98 in rolling contact with dielectric layer 75. FIG. Advantageously, roller 98 has an elastomeric outer surface. It is indicated by the reference numeral 71 in FIG. The electrostatic image forming means for forming an electrostatic image on the dielectric layer 75 will be specifically explained below. This electrostatic image forming means 71 is composed of an ion generator and an extractor, and basically includes a pair of electrodes separated by a solid dielectric member, but adding a third electrode provides various advantages. There is. FIG. 4 shows a case where a pair of electrodes are provided, and an AC power source 103 is used to connect a solid dielectric material 101 to each conductive electrode (excitation electrode and control electrode) 102-
1 and 102-2. An electrical discharge occurs when the edge electric fields Ea and Eb in the air gaps 104-a and 104-b are greater than the breakdown electric field of the air, resulting in a region 101-a adjacent to the electrode end.
Charging of the dielectric 101 occurs at 101-b and 101-b. When the alternating potential of the power source 103 is reversed, the polarity of the charges in the destruction regions 101-a and 101-b is changed. Thus, the generator 100 of FIG. 3 produces two air gap breakdowns per cycle of applied alternating potential by power supply 103, thus producing an ion supply of alternating polarity. The extraction of ions resulting from generator 100 of FIG. 4 is illustrated by generator-extractor 110 shown in FIG. Generator 110A in this example includes conductive electrodes (excitation and control electrodes) 112-1 and 1.
A solid dielectric 111 is interposed between 12-2. In order to prevent air gap destruction near the excitation electrode 112-1, this electrode 112-1 is covered with an insulating material 113.
covered with. The alternating potential is applied to the conductive electrodes 112-1 and 112-2 by the AC power supply 114A.
put it in between. Additionally, control electrode 112-2 covers region 111-r of dielectric 111 to provide an ion source.
Hole 112-h where desired air gap failure occurs
has. Ions formed in the hole 112-h can be extracted by applying an external electric field between the electrode 112-2 and the grounded auxiliary electrode 112-3 using a DC potential applied by the DC power supply 114-B. can.
An exemplary insulating surface charged by the ion source in FIG. 5 is dielectric (xerographic) paper 115 consisting of a conductive base 115-p coated with a thin dielectric layer 115-d. When switch 116 is switched to position x and one terminal of power supply 114A is grounded as shown, control electrode 112-2 is also at ground potential and no external field exists in the area between ion generator 110A and dielectric paper 115. not exist. However, switch 11
6 to position y, the potential of the DC power source 114B is applied to the control electrode 112-2, creating an electric field between the ion generator 110-A and the back surface of the dielectric paper 115. As a result, ions are extracted from the gap destruction region and charged on the surface of the dielectric layer 115-d. Many materials can be used for dielectric layer 111. Possible choices include aluminum oxide, glass enamel, ceramics, plastic film and mica. Aluminum oxide, glass enamel and ceramics require AC power source 1 for excitation.
Difficulties arise in making layers thin enough (ie, about 1 mil) so that 14A does not have to be at high pressure. Plastic films containing polyimides, such as Kapton®, and nylon, are prone to deterioration as a result of exposure to chemical byproducts of the void destruction process in holes 112-h, particularly ozone and nitric acid. Mica does not have these drawbacks and is therefore the preferred material for dielectric 111. Muscovite mica, H ₂ KAl ₃
(SiO ₄ ) ₃ is particularly preferred. In the apparatus of the present invention, a matrix ion generator 130 shown in FIG. 6 can be used. This generator 130 includes a dielectric sheet 131
A pair of gap breaking electrodes 132- are provided on one side of this sheet 131 and have holes 135 formed therein.
1 to 132-4, and a separate selector (control electrode) provided on the other side and consisting of a set of selector bars 133-1 to 133-4. The holes of each gap breaking electrode are arranged to correspond to the finger electrodes 132. When an alternating current voltage is applied between a given selector bar and the ground, ions are generated in the hole where the selector bar and the finger electrode intersect. Ions can be extracted from this hole by applying a high alternating voltage to the selector bar and a direct voltage between its finger electrode and the counter electrode of the dielectric surface to be charged. For example, the matrix location can be determined by applying a high frequency voltage between the selector bar 133-3 and the ground, and at the same time applying a DC voltage between the gap breaking electrode 132-2 and the opposing electrode of the dielectric light receiving member. 135 ₂₃ is printed. In this case, the unselected gap breaking electrodes and the counter electrode of the dielectric member are maintained at ground potential. By multiplexing dot matrix arrays in this manner, the number of voltage drivers required is significantly reduced. For example, if you want to print a dot matrix column across an 8" wide area with a dot matrix resolution of 200 dots/inch, you will need 1600 generators if you do not use multiplexing. Dew.
For example, by using the array of Figure 12 with 20 alternating frequency generating fingers, only 80 finger electrodes are required and the total number of generators is
Decreased from 1600 to 100. To prevent gap breakdown from the finger electrodes to the dielectric sheet 131 in areas not associated with the holes 135, it is desirable to coat the ends of the finger electrodes with an insulating material. The occurrence of unnecessary air gap destruction around the finger electrodes can be prevented by wrapping these electrodes. In constructing and operating matrix ion generators of this type, it is desirable to maintain substantially uniform levels of ion flow generated at the various matrix intersection points. Since a lower ion flow occurs in holes 135 where the dielectric sheet 131 is thicker, a change in the thickness of the dielectric sheet 131 causes a commensurate change in the ion outflow power. It is a particularly advantageous property of mica that it has a natural tendency to exfoliate along planes of very uniform thickness, making it particularly suitable for the matrix ion generator illustrated in FIG. Become. In this respect, the uniformity of the thickness of the dielectric sheet 131 is much more important than the actual value of its thickness. The present invention can be used to create rectangular areas of charge using the geometry of module 140 shown in FIG. In this device, charging electrodes 142-1 and 142-2 are connected to dielectric member 141.
separated from electrode 142-3 by electrode 142-3.
-3 is covered with an insulating material 145. Electrode 1
The region between 42-1 and 142-2 applies high frequency AC voltage to electrodes 142-1 and 142-2 and electrode 1.
42-3, it becomes a slot for forming an air gap discharge. The charging train of FIG. 7 can be used in plain paper copiers to replace the corona commonly found in such copiers. FIG. 8 illustrates a variation of an ion generator 160 applicable to the apparatus of the present invention for use in charging or discharging insulating surfaces. In FIG. 8, the slotted electrodes 142-1 and 142-2 of FIG. 7 are replaced by longitudinal elements 162-a.
An open mesh screen (control electrode) 162-2 having lateral elements 162-b and 162-b is used. Excitation electrode 162-1 and control electrode 162-
2 by a dielectric sheet 161, and the air gap breakdown voltage is provided by an AC power source 163. Generally speaking, the relationship between the electrode voltage and the voltage on the ion receiving surface, such as paper, is shown in Figures 5 to 7.
For a charging system of the type shown, this would typically be as shown in FIG. The electrode voltage is a DC voltage applied between the electrode in which the hole is formed and the counter electrode on the surface of the dielectric to be charged. Paper voltage is the electrostatic latent image potential of a charged dielectric member, for example dielectric (electrophotographic) paper. The above examples of use of the ion generation system of the present invention illustrate its wide applicability. In general, any current system corona line or point can be replaced by the device of the present invention. In addition to the applications described, the methods and apparatus of the present invention can be used in numerous other applications not described, such as applications related to electrostatic separation and coatings. EXAMPLES The foregoing description explains the general principles and features of the invention. The following specific and non-limiting examples illustrate specific applications of the invention. Example 1 A 1 mil stainless steel foil is laminated to both sides of 1 mil muscovite mica. Stainless steel foil is coated with resist, and the diameter of approx.
Photoetch in a pattern similar to that shown in Figure 12 with holes or holes in the 0.015 cm fingers. This provides a charging head that can be used to generate a dot matrix character electrostatic latent image on dielectric paper according to FIG. 2 with a negative voltage of 400 volts on the perforated finger electrode and a peak at a frequency of 500 kHz applied between the finger electrode and the counter electrode.
Charging occurs only when a kilovolt alternating potential is simultaneously present. A gap of 0.020 cm is maintained between the print head assembly and the dielectric surface of the xerographic sheet. The duration of the printing pulse is 20 microseconds.
It is found that under these conditions an electrostatic latent image of approximately 300 volts is produced on the dielectric sheet. This image is then toned and fused to provide a dense dot matrix character image. from charging head
The ionic current extracted from this charging head, collected by electrodes spaced 0.020 cm apart, is found to be 1 milliampere per square centimeter. The charging head has a lifetime of approximately 2000 hours. Example 2 Example 1 is repeated using a polyimide derivative instead of muscovite mica. As mentioned above, 1
Mil stainless steel foil is laminated to 1 mil thick ^Kapton® polyimide film. The same results as in Example-1 are obtained at an applied high frequency potential of 1.5 kilovolt peak. The charged head provides a lifespan of approximately 50 hours. Example 3 The present invention is applied to obtain a continuous toned image by extracting a large number of ions from a charging head per unit time in proportion to the applied ion extraction potential. This is illustrated in Figure 9, where the apparent surface potential on the dielectric surface is plotted as a function of the potential difference between the ion generating electrode and the dielectric counter electrode. Ion generating electrode dielectric surface gap is 0.015
cm, and the charging time is 50 microseconds. B Three-Electrode Embodiment The matrix image ion generator 130 shown in FIG. 6 is advantageously incorporated into an electrostatic printing device. However, the ion generator and extractor 110 shown in FIG. 5 can be used to form an electrostatic image on a dielectric surface and to discharge such an image. Thus, with further reference to FIG. 5, when switch 116 is closed at y, electrode 112-2 is held at a positive potential V ₁ and a positive electrostatic latent image of smaller magnitude V ₂ is placed on surface 115-d. It is formed. However, if switch 116 is in position x and the previously formed electrostatic latent image is below hole 112-h, generator 110A behaves as an erase unit. This phenomenon is further explained at 200 in FIG. 10 in connection with the dot matrix printing embodiment of FIG. At time t ₁ , a predetermined hole 185 ₂₃ on matrix ion generator 130 (FIG. 6)
is energized by a DC pulse that creates a negative potential on electrode 132-2, while a high frequency potential is applied to selector bar 132-3. This is a dielectric surface 2 with bucking electrodes 202.
The polarity occupying regions 203 and 204 on 01 causes the formation of a negative electrostatic dot image. At a later time t ₂ , hole 135 ₂₃ forms areas 204 and 2
05, the selector bar 133-3 is further energized, but no charging is desired so the negative pulse is applied to the finger electrode 132-3.
2 is not applied. However, the presence of a negative electrostatic image in region 204 attracts positive ions from hole 135 ₂₃ , erasing the image previously formed in this region. Adding a third electrode to the two electrode structures described above alleviates this problem and provides additional benefits in terms of controlling the size and shape of the electrostatic image formed by this type of ion generator. It was found that it brings about An ion generator 210 according to this three-electrode embodiment is shown in cross-section in FIG. The ion generator 210 is a solid dielectric layer 2
includes an excitation electrode 211 and a control electrode 215 separated by 13. AC power source 212 is used to provide a gap break in hole 214. A third screen electrode 219 is separated from the control electrode by a second dielectric layer 217. 3
The terminology adopted for the electrodes draws similarities to vacuum management theory. The terms "excitation" electrode and "control" electrode can effectively be extended to equivalent electrodes in two basic electrode embodiments. The second dielectric layer 217 advantageously covers the holes 214 of the control electrode.
It has a substantially larger hole 216. This is necessary to avoid wall charging effects. Screen electrode 219 includes a hole 218 located at least partially below hole 214 . In electrophotographic matrix printing machines,
For example, the excitation and control electrodes can be selector electrodes and the finger electrodes of FIG.
The screen electrode can then consist of an additional finger electrode with holes that match the pattern of the control electrodes or a continuous perforated metal plate or other member whose openings are adjacent to all the printed holes. The latter embodiment of the screen electrode is, for example, an open mesh screen.
It can take the form of a screen). The application of the ion generator described above in electrophotographic matrix printing is illustrated in FIG. 12th
The figure shows the ion generator 210 of FIG. 21 used with a dielectric paper 220 consisting of a conductive base coated with a dielectric layer 221 and backed by a grounded auxiliary electrode 225. When switch 222 closes at position Y, dielectric layer 2
There is simultaneously an alternating potential across 13, a negative potential V _C on control electrode 215 and a negative potential V _S on screen electrode 219. The negative ions in the holes 214, as in the two-electrode embodiment, are subjected to an accelerating electric field that causes them to form an electrostatic latent image on the dielectric surface 221. The presence of a negative potential V _S on the screen electrode 219, chosen such that V _S is smaller in absolute value than V _e , does not prevent the formation of an image that would have a negative potential V _i (less than V _C in absolute value). . Due to the previously formed electrostatic image of the switch 222 at position X and the negative potential V _i partially below the hole 214, partial erasure of the image will occur in the absence of the screen electrode 219. However, the screen potential V _S is chosen such that V _S is greater in absolute value than V _i , so the presence of electrode 219 prevents the passage of positive ions from hole 214 to dielectric surface 221 . The inclusion of screen electrode 219 in the ion generator of the present invention provides advantages beyond preventing image discharge under the conditions described above. Screen electrodes can be used alone or in conjunction with control electrodes to control matrix imaging. V _S
=0, no latent image is generated due to the above discharge phenomenon. Therefore, three-level matrix image control is possible in the device according to the invention. Screen electrode 219 provides unexpected control over image size. Using the dot matrix printing configuration shown in FIG. 6 overlaid with finger screen electrodes in accordance with the present invention, image size can be controlled by varying the size of the screen holes 218. Further, with all variables held constant except screen potential 226, and using such a geometry, it has been found that larger screen potentials produce smaller dot diameters. This technique can be used to create elaborate and structured images. With the correct selection of V _S and V _C ,
This allows the distance between the ion generator 210 and the dielectric surface 221 to be increased while maintaining a constant dot image diameter. This is achieved by increasing the absolute value of V _S while keeping the potential difference between V _S and V _C constant. Image shape can be controlled by using a predetermined screen electrode overlag in a matrix electrophotographic printer. Screen holes 218 may take the shape of fully formed characters, for example, no larger than corresponding round or square control holes 214. The electronic wiring diagram used to control the electrophotographic printing apparatus of FIG. 12 allows the system to be biased as shown in the circuit diagram of FIG. Element 231 is a pulse generator. The magnitude of the control pulse can be varied to produce the desired V _C and V _S by choosing the appropriate bias potential. For example, the following combinations all produce V _S =-700 volts and V _C =-800 volts. 1 V bias = -600 volts; ΔV _S = -100 volts; ΔV _C = -200 volts 2 V bias = -500 volts; ΔV _S = -200 volts; ΔV _C = -300 volts 3 V bias = -400 volts; ΔV _S = -300 volts; ΔV _C = -400 volts4 V bias = -300 volts; ΔV _S = -400 volts; ΔV _C = -500 volts5 V bias = -200 volts; ΔV _S = -500 volts; ΔV _C = -600 volts The above advantages are further illustrated with respect to the following non-limiting example; Example 4 A 1 mil stainless steel foil is laminated to both sides of a 1 mil muscovite mica sheet. Coat the foil with resist and have a diameter of approximately 0.015cm.
Photoetch in a pattern similar to that shown in FIG. 6 with holes or holes. thickness
0.015 cm of the mica layer of FIG. 2 is bonded to the foil according to FIG. A screen electrode with 0.0375 cm diameter holes in the same pattern as the finger pattern is photoetched from 1 mil stainless steel, and the fingers and screen holes are concentrically bonded to the second mica layer. This structure uses a 1 kilovolt peak alternating current potential 212 at a frequency of V _C -500 volts, V _S -400 volts and 500 kilohertz to create an electrostatic latent image on a dielectric paper as shown in FIG. It is equipped with a charging head that is used to apply a charge. A gap of 0.015 cm is maintained between the print head assembly and dielectric surface 221. V _C takes the form of a printing pulse of 20 microseconds duration. Under these conditions, a latent image in the form of a dot of approximately -300 volts is produced on the dielectric sheet. This image is then toned,
Fusing to obtain a precise dot matrix character image. The ionic current extracted from the discharge head, collected by an electrode 0.015 cm from the head, is 1
It is found to be 0.5 milliamps per square centimeter. However, even if screen electrode 219 is omitted, the electrostatic image under the control electrode will be erased unless a printing pulse is applied. Example 5 The electrophotographic printing apparatus of Example 4 was tested with various diameters of screen holes 218 and the dimensions of the resulting electrostatic dot images were measured. The results below are representative. Screen hole diameter (cm) Dot image diameter (cm) 0.038 0.038 0.025 0.030 0.020 0.025 In general, a reduction in screen hole size can cause a corresponding reduction in latent image size without any compromise in image charging. discovered. Example 6 The electrophotographic printing apparatus of Example 4 was tested at various screen potentials and _Vs , and the dimensions of the resulting electrostatic dots were measured. The results below are representative. Screen potential (volts) Dot image diameter (cm) −300 0.055 −400 0.043 −500 0.030 −600 0.020 In general, increasing the potential on the screen reduces the latent image size without any compromise in image charging. It was discovered that this could be done. Example 7 The electrophotographic printing device of Example 4 was tested using various gaps between the print head assembly and the dielectric surface 221. By varying the screen potential, V _S , and keeping the potential difference between V _S and V _C constant, the dimensions of the resulting electrostatic dot image were held constant. The results below are representative:

[Table] In general, it has been found that increasing the screen potential V _S by increasing the gap from the print head assembly to the dielectric surface provides a constant dot image diameter without any compromise in image charging. Served. Example 8 The electrophotographic printer of Example 1 was modified so that the screen had holes 48 in the form of slots instead of holes. The toned electrostatic latent image obtained was oval in shape. V Impregnation of anodized aluminum member As mentioned above, the surface 27 of the image roller 25 (first
) and image roller 7 in the electrophotographic system shown in FIG.
It is preferred to use a dielectric material as surface 75 of 3 (in the electrostatic printing system of FIG. 1) that satisfies certain criteria. These criteria include high resistivity, high abrasion resistance, smooth finish and high modulus. A preferred material is anodized aluminum oxide impregnated by the method described below. Removal of absorbed water from the oxide layer of anodized aluminum structures can be accomplished using either heat, vacuum, or storage of the material in a desiccator. Although all three methods are effective, the best results are achieved by heating in a vacuum, for example in a vacuum oven. Alternatively, the articles to be treated can be stored for several hours in a dry box containing a desiccant. It is preferred that the oxide be thermally treated prior to impregnation at a temperature below 150°C, preferably at a temperature not exceeding 100°C.
At higher temperatures, some cracking of the oxide occurs due to the high coefficient of thermal expansion of the aluminum substrate. After removing the absorbed water from the oxide coating, it can be impregnated with an organic resin.
However, since the use of solvent coatings leaves residual solvent in the pores, it is preferred to use completely solid systems. Liquid resins that can be crosslinked to provide hard solid coatings are thus particularly advantageous materials. Such resins can be cured either by thermal or radiation crosslinking. It is also desirable that the resin have low shrinkage and low moisture absorption after curing. In order to be able to diffuse the organic resin into the porous structure within a reasonable period of time, it is advantageous to use a liquid crosslinking system with a viscosity below 500 centipoise. These aforementioned techniques can be used to process solid aluminum cylinders with impregnated oxides for use in electrostatic imaging. In such systems, the electrostatic charge is then toned as disclosed in, for example, U.S. Pat. No. 3,662,395;
The toned image is then transferred to plain paper. Table 2 of that patent shows that porous aluminum oxide surfaces sealed with Teflon are unsatisfactory for electrostatic imaging due to low breakdown voltage and low pore insulation resistance and coating hardness. A drum coated with an insulating film capable of supporting electrostatic charges has been awarded a U.S. patent.
Disclosed in No. 3907560. The dielectric surface is a barrier layer aluminum oxide film. This is because the porous anodized aluminum oxide layer is stated to function as a conductor rather than as a dielectric. Although the barrier layer anodized aluminum film is a good insulator, its nonporous nature limits the maximum thickness of the barrier layer film to the range of 1/2 to 1 micron.
At this thickness, the maximum voltage that the layer will support is limited and the surface is not rigid in the conventional sense. This is because localized strains are propagated through this thin film with subsequent deformation of the aluminum substrate. The limits of thin barrier films are overcome by the use of dual anodized aluminum coatings, as described in US Patent No.
Overcome in Nos. 3937571 and 3940270.
This coating is produced by electrolytically oxidizing the aluminum surface, followed by subsequent electrolytic oxidation under conditions that produce a barrier aluminum oxide layer. This not only increases the complexity of processing the anodized layer, but the limiting thickness is approximately 20
microns, and the surface potential at which the oxide layer can be charged is up to 620 volts. In contrast to the prior art, the present invention provides a simple and reliable technique for fabricating oxide films with thicknesses as large as 100 microns and capable of supporting thousands of volts. The advantages of the invention will become clearer from the following non-limiting examples. Prior Art Example A cylinder made from aluminum alloy 7075-T6 was hard coat anodized in sulfuric acid according to the teachings of Wernick and Pinner. The final thickness of the anode layer was 60 microns. The anodized cylinder is expressed by formula 1 in the table below.
It was sprayed with an ultraviolet curable resin system according to the following. This low viscosity liquid appeared to impregnate the pores within a period of 1 minute. After a few minutes, the surface of the cylinder was wiped clean of excess liquid and the impregnated cylinder was cured by exposure to radiation from a medium pressure mercury arc lamp. After radiation curing, the cylinder was polished with 600 grit abrasive paper to remove any 3 or 4 micron oxides to a 10 microinch finish. A test rig was used to generate an electrostatic charge on the surface of the aluminum oxide layer. A corona ion source was used to charge the surface and a feedback electrometer was used to measure the surface potential. At the highest charge level used, voltages of only a few volts were evident on the surface. This potential decayed to zero in about 1 second. The dielectric strength of this layer is determined by placing a light weight electrical contact with a radius of curvature of 1.25 cm on the surface of the aluminum oxide and applying a high electric potential between this electrode and the aluminum substrate through the layer. It was determined by gradually increasing the amount of water until it was pulled out. Using both direct and alternating current and determining the breakdown potential at multiple locations, the breakdown voltage was determined to be in the range of 900-1200 volts. Thus, both the charge level and the dielectric strength achieved with this prior art embodiment were unsatisfactory. The following examples are presented in the form of a table below, illustrating the advantages of the present invention over the prior art.

[Table] Heat

【table】

Table: In all examples in Table 1 involving heating of the aluminum, the impregnation was carried out using still warm (40-55° C.) aluminum. The vacuum oven-treated sample was cooled to the processing temperature while being held in vacuum. Although vacuum impregnation with an organic resin was not attempted, heating in a vacuum oven followed by vacuum impregnation of the anodic coating would give the excellent electrical properties shown by the above examples using the method of the invention. That is clear. Having described various aspects of the invention, it is to be understood that the foregoing detailed description is for the purpose of illustration, and that modifications of various parts and equivalent substitutions of components shown and described are within the scope of the claims. It will be understood that what may be done without departing from the spirit and scope of the invention as described.

[Brief explanation of the drawing]

FIG. 1 is a simplified diagram of the entire image forming apparatus as an electrophotographic apparatus according to a preferred embodiment of the first basic embodiment of the present invention. FIG. 2 is a partial sectional view showing an electrostatic charge erasing unit used in the image forming apparatus shown in FIG. FIG. 3 is a partial sectional view showing a modification of the electrostatic erasing unit. FIG. 4 is a simplified cross-sectional view of an imaging ion generator used in an apparatus according to the invention. FIG. 5 is a simplified cross-sectional view of an ion generator and extractor according to the invention. FIG. 6 is a plan view of a matrix ion generator for electrostatic dot matrix printing. FIG. 7 is a perspective view showing a cross section of a charge transfer member using a light receiving member assembly according to a modification of the present invention. Figure 7 shows
FIG. 1 is a partial perspective view showing the physical form of an ion generator according to the present invention. FIG. 8 is a sectional view showing a modification of the ion source according to the present invention. FIG. 9 is a diagram showing the relationship between electrode voltage and paper voltage in the ion generation method of the present invention. FIG. 10 is a perspective view showing a toned electrophotographic image on a dielectric member backed with a conductor produced by the matrix ion generator of FIG. 6; FIG. 11 is a simplified cross-sectional view of an ion generator according to a modified embodiment of the invention. Figure 12 shows the first
2 is a simplified cross-sectional view of an ion generator and an extractor using the specific example of FIG. 1. FIG. FIG. 13 is a simplified diagram showing a modification of the circuit used in the ion generator and extractor of FIG. 12.

Claims (1)

[Scope of Claims] 1. An image forming member having a dielectric surface layer and a counter electrode provided on the back surface thereof, an electrostatic image forming means for forming an electrostatic image on the image forming member, and the image forming member. An image forming apparatus comprising: means for developing an electrostatic image formed on a member; and pressure transfer means for transferring the developed image formed on the image forming member onto an image receiving member under pressure, An electrostatic image forming means is formed by applying an alternating potential between an excitation electrode and a control electrode separated by a solid dielectric member, and a joint between an end surface of the control electrode and the solid dielectric member. means for generating ions in an air region; and means for applying a DC voltage Vc between the control electrode and the counter electrode to extract ions from the air region to form an electrostatic image on the imaging member. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the image forming member comprises a rotatable image forming drum. 3. The image according to claim 1, further comprising a scraper blade for removing residual toner on the image forming member and a charge eliminating means for removing residual electric charge on the image forming member. Forming device. 4. an image forming member having a dielectric surface layer and a counter electrode provided on the back surface thereof; an electrostatic image forming means for forming an electrostatic image on the image forming member; An image forming apparatus comprising means for developing an electrostatic image, and pressure transfer means for transferring the developed image formed on the image forming member onto an image receiving member under pressure, wherein the electrostatic image forming means comprises: , applying an alternating potential between an excitation electrode and a control electrode separated by a solid dielectric member to induce ions into an air region formed by a junction between an end face of the control electrode and the solid dielectric member; means for extracting ions from the air region by applying a DC voltage Vc between the control electrode and the counter electrode, and disposed between the control electrode and the imaging member. An image characterized by comprising means for applying a DC voltage Vs between a screen electrode having holes and the counter electrode to control extraction of the ions and forming an electrostatic image on the image forming member. Forming device.